Multiple fuel jet burner and torch igniter unit with fuel vaporizing tubes



951 F. D. M. WILLIAMS 2,541,900

MULTIPLE FUEL JET BURNER AND TORCH IGNITER UNIT WITH FUEL VAPORIZINGTUBES Filed Dec. 24, 1948 2 Sheets-Sheet 1 ,HHHII 1 O (D Q B O 0 I 1INVENT'OR .740. 7. V/LLI/i'llli Feb. 13, 1951 F. D. M. WILLIAMS2,541,900

MULTIPLE FUEL JET BURNER AND TORCH IGNITER UNIT WITH FUEL VAPORIZINGTUBES Filed Dec. 24, 1948 2 Sheets-Sheet 2 ttoagy Patented Feb. 13, 1951MULTIPLE FUEL JET BURNER AND TORCH IGNITER UNIT WITH FUEL VAPORIZINGTUBES Frederick D. M. Williams, Nobel, Ontario, Can

ada, assignor to A. V. Roe Canada Limited, Malton, Ontario, Canada, acorporation Application December 24, 1948, Serial No. 67,118

Claims. (Cl. 60-44) This invention relates to improvements in burnersfor the combustion chambers of gas turbine engines and to the ignitersassociated therewith.

Air is the working medium of a gas turbine.

engine and it is introduced into the engine by means of a compressor,heated in the combustion chamber and then directed to the turbine toperform useful work. The exhaust from the turbine may be used to give apropulsive thrust and I chamber it is heated directly by the burning offuel introduced into the stream by means of an injector, commonly knownas the burner. Combustion takes place within an inner liner of thecombustion chamber, known as the flame tube, which is designed tocontrol the combustion and to achieve the most efiicient heating of theair charge. In operation, combustion is continuous; the fuel-air mixturebeing ignited by the gases which are already burning. But t start andestablish this type of combustion, the engine must be turned by means ofa starter to generate a flow of air through the combustion chamber and,at a predetermined speed, fuel must be ill-- jected into the air streamand the resulting mixture ignited by means of an electric spark. Oncestarted by this m ans combustion becomes continuous and the igniter isno longer required and may be. switched off.

It will be readily understood that continuous combustion such as I havedescribed would be impossible if all the burning gases were carrieddownstream at a speed greater than that of flame propagation, and inpractice, due to the high speed of the air stream, it is necessary toarrange a small region of reverse flow into which fuel may beintroduced. There are two conventional methods of arranging thisstabilizing zone, namely the upstream injection of the fuel into thewake of a bafile' suitably situated in the air stream, and thedownstream injection of the fuel into a region of low pressure in thecentre of the flame tube, created by an air swirler. Clearly the ideallocation of the igniter is in the centre of the stabilizing zone andwith the upstream injection method it is sometimes possible to situatethe igniter in the centre of the baffle. However, with the downstreaminjection method the ideal location for the ignlter is occupied by theburner itself and the igniter has to be set as conveniently as possiblein the side of the flame tube.

The foregoing refers to systems in which liquid fuel is injecteddirectly into the flame tube. However more satisfactory burning may beobtained by what is knownas the vapor combustion system, that is by thevaporization of the fuel, its preheating and-mixture with a certainamount of air, before its entry into the flame tube. This vaporizationand preheating is .carried out in vaporizer tubes, which are circulartubes installed longitudinally in the combustion chamber and mounted ona bafile at the upstream end thereof. The downstream ends of thesevaporizer tubes are bent through 180. Liquid fuel is injected into theupstream ends, which are open and exposed to the air stream from thecompressor, and the mixture is carried down the tubes and dischargedinto the flame tube in an upstream direction. The flame of thesubsequent combustion of the mixture, before being carried awaydownstream, plays upon the vaporizer tubes as they enter the flame tube,thereby promoting vaporization and preheating of the fuelair mixturewithin them.

In the vapor combustion system, the vaporizer tubes occupy the centre ofthe flame tub-e so that again it is difiicult to find a satisfactorylocation for the igniter. Furthermore, starting is ren.. dered difficultby the fact that there are no provisions for preheating the tubes beforecombustion has started.

The object of this invention is to improve the methods of igniting thecharge of a combustion system employing the vapor combustion principleand to insure more positive starting over a wide range of inletvelocities. A further object of the invention is to furnish in one unita fuel injector and an igniter which are thus readily accessible forremoval, for maintenance and 121- spection purposes.

Other objects and advantages of this invention will be apparent duringthe course of the following description.

Fig. 8 is an end elevation of the combination burner torch igniterviewed from downstream. and

Fig. 4 is a sectional side elevation, of the combination burner torchigniter on the line l'l in Fig. 3.

It will be seen from Fig. 1 that the principal components of thecombustion chamber are the outer casing 5, the flame tube 6 and thevaporizer tubes 1. The direction of flow of the air stream passingthrough the combustion chamber is from left to right of Fig. 1. At theupstream end of the flame tube is a baffle 8 upon which the vaporizertubes are mounted, as shown particularly in Fig. 2. The flame tube isperforated by a number of holes throughout its length for the purpose ofadmitting air from the outer casing into the flame tube, to control themanner in which combustion takes place.

The fuel injector is illustrated in detail in Fig. 4. It comprises aninjector head 9 containing six straight jets I and a swirl-typeatomizing jet I I. In addition, the injector head carries two electrodesI2 and I3 one of which is mounted directly on the head and the otherconnected by a high tension lead, through the tube I4 to a terminal I5mounted on the outside of the combustion chamber. The atomizing jet IIis fed by a fuel line I6 which in this example runs substantiallyparallel to the aforementioned tube I4. It will be understood, however,that this is not necessary since the fuel can be introduced to theinjector from any convenient position,

which may not coincide with the most convenient.

location for the ignition terminal I5. The six main fuel jets aresituated at oblique angles around the central atomizing jet and are fedby passages within the head which, as can be seen in Fig. 4, runtogether to a common chamber II surrounding the aforementioned fuel lineI6. This chamber is in turn connected to the outer casing of thecombustion chamber by a line I8, coaxial with the line IE but of asubstantially greater diameter, so that fuel can pass down the annularspace between them.

Fig. 2 indicates the arrangement of the injector head 9 in relation tothe vaporizer tubes. The ignition electrodes I2 and I3 protrude throughthe baflle 8 and the atomizing jet II, which is located in a recess inthe head immediately below the aforementioned electrodes, is also givendirect access into the flame tube 6. The six main jets I0 are arrangedto discharge into the mouths of the six vaporizer tubes but theydischarge into these tubes obliquely so that a substantial area of eachtube is exposed to the direct flow of air from the compressor.

In order to start the engine the starter motor is energized and turnsover the compressor thereby delivering air to the combustion chamher.The rotation of the compressor also has the effect of driving the fuelpump and when the fuel pressure reaches a predetermined value, the fuelsupply to the atomizing jet II is turned on. In addition, the electricalsystem is energized so that current beings to flow across the spark gapof the electrodes I2 and I3. A flne 5 spray of fuel emerges from theatomizing jet and is delivered across the electrodes into the combustionchamber. This spray is ignited by the spark, producing a flame centrallylocated among the vaporizer tubes and playing upon them.

Under the action of the compressor air is flowing rapidly through thecombustion chamher, and part of it is directed by the baille I into themouths of the vaporizer tubes, whence it is carried down the tubes anddischarged upstream into the low pressure region in the wake 5 of thesaid baffle. When the main fuel supply is turned on, the fuel flowsthrough the annulus between the lines I6 and I8 into the chamber I1, andthence through the six jets I0 into the vaporizer tubes. During itspassage through the tubes, the liquid fuel is vaporized and mixed withthe air; vaporization is assisted by the heat of the flame of theatomizing jet playing upon the outside of the tubes. Thus a preheated,combustible mixture emerges from the vaporizer tubes and is readilyignited by the pilot flame, burning from the atomizing jet.

Thereafter combustion becomes continuous, the mixture entering the flametube being ignited by the flame of the gas already burning,

The vaporizer tubes are fully exposed to combustion in the flame tube sothat the gas, entering through these tubes is preheated, and in turn theliquid fuel, running down the inside of the tubes and being vaporized onthe hot surfaces, serves to cool the tubes against burning. There is nofurther need for the igniter, and the current may be switched off andthe fuel supply to the atomizing jet discontinued.

It is to :be understood that the form of my invention, herewith shownand described, is to be taken as a preferred example of the same:various changes in the shape, size and arrangement of the parts may beresorted to, and, for example, the igniter may take the form of a glowplug or a spark gap, without departing from the spirit of my inventionor the scope of the claims.

What I claim as my invention is: 1. In a combustion chamber of a gasturbine engine, a flame tube in which combustion takes place, openingsin the flame tube for admitting a stream of air at one end of the flametube to support combustion, vaporizer tubes mounted in the flame tubeadjacent the upstream end of the flame tube and extending longitudinallythereof, each such vaporizer tube having an inlet end exposed to the airstream through the combustion chamber and an outlet end discharging intothe flame tube, and an injector head located substantially on thelongitudinal axis of the flame tube at its upstream end, said injectorhead having a centrally located igniter jet directed into the flame tubesubstantially at the longitudinal axis thereof between the vaporizer 55tubes, whereby an igniting flame may be injected directly into the flametube and played upon the vaporizer tubes, an igniter mounted on the headin front of said igniter jet, a plurality of fuel supply jets arrangedaround the igniter 60 jet and directed to the inlet ends of thevaporlze'r-tubes, said injector head being provided with a chamber,oblique passageways from the fuel supply jets to the chamber, and apassageway from the igniter jet, and having a fuel inlet con- 05 duitcommunicating with said chamber for conducting fuel to the fuel supplyjets, and a fuel inlet conduit communicating with the passageway to theigniter jet to conduct fuel to said igniter jet.

70 2. In a combustion chamber of a gas turbine engine, a flame tube inwhich combustion takes place, openings in the flame tube for admittingbefore that flame is carried away downstream.

flame tube and extending longitudinally thereof, each such vaporizertube having an inlet end exposed to the air stream through thecombustion chamber and an outlet end discharging into the flame tube,and an injector head located substantially on the longitudinal axis ofthe flame tube at its upstream end, said injector head comprising anigniter jet directed into the flame tube substantially at thelongitudinal axis thereof between the vaporizer tubes, whereby anigniting flame may be injected directly into the flame tube and playedupon the vaporizer tubes, an igniter situated in front of said jet, aplurality of fuel supply jets arranged around the igniter jet anddirected to the inlet ends of the vaporizer tubes, a fuel inlet conduitfor the fuel supply jets, and a fuel inlet conduit for the igniter jetwithin and substantially co-axial with the fuel inlet conduit for thefuel supply jets.

3. .In a combustion chamber of a gas turbine engine, a flame tube inwhich combustion takes place, openings in the flame tube for admitting astream of air at one end of the flame tube to support combustion,vaporizer tubes mounted in the flame tube adjacent the upstream end ofthe flame tube and extending longitudinally thereof. each such vaporizertube having an inlet end exposed to the air stream through thecombustion chamber and an outlet end discharging into the flame tube,and an injector head located substantially on the longitudinal axis ofthe flame tube at its upstream end, said injector head comprising a bodymember having a centrally located igniter jet directed'into the flametube substantially at the longitudinal axis thereof between thevaporizer tubes, whereby an igniting flame may be injected directly intothe flame tube and played upon the vaporizer tubes, a plurality of fuelsupply jets arranged around the igniter jet and directed to the inletends of the vaporizer tubes the injectorhead being provided with, acentral fuel inlet passage, oblique pass w ys from the fuel supply jetsto said central passage, and a passageway from the igniter jet openinginto the aforesaid central passage, and the head having secured theretoa fuel inlet conduit communicating with the aforesaid central passagefor conducting fuel to the fuel sup- Ply jets, and another fuel inlet ofsmaller diameter extending through the first mentioned inlet conduit andthe aforesaid central passage and communicating with the passageway tothe igniter jet to conduct fuel to said igniter jet, and an ignitermounted on the head in front of said igniter jet.

4. In a combustion chamber of a gas turbine engine, a flame tube inwhich combustion takes place, openings in the flame tube for admitting astream of air at one end of the flame tube to support combustion,vaporizer tubes mounted in the flame tube adjacent the upstream end ofthe flame tube and extending longitudinally thereof, each such vaporizertube having an inlet end exposed to the air stream through thecombustion chamber and an outlet-end discharging into the flame tube,and an injector head located substantially on the longitudinal axis ofthe flame tube at its upstream end, said injector head having acentrally located recess in its discharge end in which is mounted anigniter jet directed into the flame tube substantially at thelongitudinal axis thereof between the vaporizer tubes, whereby anigniting flame may be injected directly into the flame tube and playeduponthe vaporizer tubes, an igniter mounted on the head at the open endof the igniter jet recess in front of said igniter jet, a plurality offuel supply jets arranged around the igniter jet and directed to theinlet ends of the vaporizer tubes, said injector head being providedwith a chamber, oblique passageways from the fuel supply jets to thechamber, and a passageway from the igniter jet, and having a fuel inletconduit communicating with said chamber for conducting fuel to the fuelsupply jets, and a fuel inlet conduit communicating with the passagewayto the igniter jet to conduct fuel to said igniter jet.

5. In a combustion chamber of a gas turbine engine, a flame tube inwhich combustion takes place, openings in the flame tube for admitting astream of air at one end of the flame tube to support combustion,vaporizer tubes mounted in the flame tube adjacent the upstream end ofthe flame tube and extending longitudinally thereof, each such vaporizertube having an inlet end exposed tothe air stream through the combustionchamber and an outlet end discharging into the flame tube, and aninjector head located substantially on the longitudinal axis of theflame tube at its upstream end, said injector head having a recess inits discharge and in which is located an igniter jet directed into theflame tube substantially at the longitudinal axis thereof between thevaporizer tubes, whereby an igniting flame may be injected directly intothe flame tube and played upon the vaporizer tubes, a pair of electrodesmounted on the head at the forward open end of the igniter jet recess,and an electrical conduit supported by the head and connected to one ofsaid electrodes, and a plurality of fuel supply jets arranged around theigniter jetand directed to the inlet ends of the vaporizer tubes.

FREDERICK D. M. WILLIAMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,404,335 Whittle July 16, 1946FOREIGN PATENTS Number Country Date 603,485 Great Britain June 16, 1948

